Field of the Invention
The present invention relates to image forming apparatuses, such as copying machines, printers, facsimile machines, and multifunction apparatuses, that employ an electrophotographic system and perform image formation.
Description of the Related Art
In the related art, a toner image formed on a recording material by using an electrophotographic process undergoes a heating and fixing treatment performed by a fixing unit. Recording materials to which toner images have been fixed are ejected to a stacking tray by a transport device. The recent increase in printing speed is one of the reasons that recording materials to which toner images have been fixed are stacked in a stacking tray while the temperatures of the recording materials are still high. In addition, when a printing operation is continuously performed, sheet members are consecutively stacked in a stacking tray before they are cooled, and as a result, toners on the sheet members may re-melt. The toners that have re-melted stick to the sheet members and toner images that are superposed with the toners. By separating the sheets, which have been stuck to each other, from each other, the toner images of plural sheets become separated from the sheets simultaneously, and a problem of missing portions of an image occurs. In addition, with the recent demands from users for power-saving products, the melting points of toners are likely to decrease, and accordingly, toners fixed to sheet members in a stacking tray are more likely to re-melt.
For example, Japanese Patent Laid-Open No. 2005-77565 describes that, in an image forming apparatus, an area in the vicinity of ejection rollers that are disposed downstream from a fixing device is cooled by a cooling fan, and that the flow of air from the cooling fan is changed in accordance with the presence or absence of a sheet-ejection device mounted on the image forming apparatus.
However, in the configuration disclosed in Japanese Patent Laid-Open No. 2005-77565, when cooling a recording material, the ejection rollers and the like are also cooled, and thus, a toner image is cooled unevenly due to differences between the temperature of a recording material that is ejected immediately after undergoing a heating and fixing treatment and the temperatures of the ejection rollers and discharge rollers. As a result, an image defect such as a contact mark formed by the ejection rollers sometimes occurs.